9 research outputs found
How the geometry makes the criticality in two - component spreading phenomena?
We study numerically a two-component A-B spreading model (SMK model) for
concave and convex radial growth of 2d-geometries. The seed is chosen to be an
occupied circle line, and growth spreads inside the circle (concave geometry)
or outside the circle (convex geometry). On the basis of generalised
diffusion-annihilation equation for domain evolution, we derive the mean field
relations describing quite well the results of numerical investigations. We
conclude that the intrinsic universality of the SMK does not depend on the
geometry and the dependence of criticality versus the curvature observed in
numerical experiments is only an apparent effect. We discuss the dependence of
the apparent critical exponent upon the spreading geometry and
initial conditions.Comment: Uses iopart.cls, 11 pages with 8 postscript figures embedde
Apparent Rate Constant for Diffusion-Controlled Three molecular (catalytic) reaction
We present simple explicit estimates for the apparent reaction rate constant
for three molecular reactions, which are important in catalysis. For small
concentrations and , the apparent reaction rate constant depends only on
the diffusion coefficients and sizes of the particles. For small concentrations
and , it is also time -- dependent. For large concentrations, it gains
the dependence on concentrations.Comment: 12 pages, LaTeX, Revised: missing ref. for important paper by G.
Oshanin and A. Blumen was added and minor misprints correcte
On the evolution of nanocluster size distribution in a nanocluster aggregation source
This paper presents a detailed model of cluster formation from a supersaturated atomic vapor in an inert buffer gas. The population balance equations for the cluster size distribution are based on the Smoluchowski coagulation equation and take into account (i) convective diffusion of clusters, (ii) cluster loss to walls of an aggregation chamber, and (iii) formation of fractal-like aggregates. The model predictions are confronted to experimental observations, and they agree with experimental data on Cu particle formation in NC200-UHV nanocluster source. The model can be used as an aid in tuning the experimental parameters for attaining a desired nanoparticle size distribution.